The present invention relates to a radial blower which has a radial wheel rotating in a spiral housing.
In order to increase the action of the controlled three-way catalysts it is known to use two methods, namely the waste gas recirculation and the secondary air supply. These methods minimize the generation of nitrogen or reduce the content of carbon monoxide and hydrocarbons before the waste gas reaches the catalyst. During the secondary air supply the waste gas supplies fresh air behind the motor in the shortest possible way to eliminate hydrocarbon compounds and carbon monoxide produced during the combustion process. Thereby post burning of the waste gas at temperatures of above 600.degree. C. is obtained. During this additional combustion process heat is supplied to the catalyst. This is especially important during "cold start" when a relatively solid mixture is driven, whereby automatically the CO- and HC-fractions are increased in an over-proportional degree. Due to the secondary air supply in the hot waste gas practically a post burning is set in progress, during which the unburnt carbon monoxide and hydrocarbon in the motor are post-oxidated or post-burnt. The secondary air supply has however another effect. The control catalyst operates optimally starting from a predetermined operational temperature. This heat phase can continue for a limited time, during which the vehicle can cover several kilometers. After the post combustion through a secondary air supply system increase in this heat phase the waste gas temperatures. The higher temperatures allow faster reaction of the G-catalyst. The G-catalyst can earlier complete its function, namely to convert the pollutants.
With the secondary air supply there is however the difficulty to provide a compact, effectively operated blower which can overcome the high pressure in the exhaust train and pump sufficiently high quantity of fresh air into the waste train. It has to be taken into account that in the motor chamber as a rule there is only little space for additional aggregates so that compact construction for an efficient blower is an especially important criterium.